Power conversion circuitry is employed in many applications, such as in portable devices using external power from a universal serial bus (USB) connection to operate the device and/or to charge internal batteries. In many instances, the current drawn from a source may need to be limited, for example, according to specifications published for devices drawing power from a USB connection. For instance, portable devices are limited to drawing at most 100 mA from a USB 2.0 connection, unless a higher limit (e.g., up to 500 mA) is negotiated. Similarly, USB 3.0 connections are typically limited to drawing 150 mA unless a higher amount (e.g., up to 900 mA) is negotiated. Accordingly, power management circuitry in many portable devices provides input power conversion with current limiting, using on-board input current sensing via a sense resistor or sense FET connected between the power input terminal and the high-side power FET. High-side current sensing may also be important in other types of power converters, such as for sensing and regulating output current flow from a boost converter or a buck/boost converter. However, the conventional current sensing approach incurs significant power loss in terms of heat generated by conduction of high-side current flowing through the sensing device. Moreover, the sensing component (e.g., resistor or FET) must be sized to accommodate the maximum level of input current, and accordingly the sensing device occupies a significant amount of space in terms of integrated circuit die area and/or external board area, thereby increasing cost. Accordingly, improved current sensing apparatus and techniques are desirable by which sensing component power dissipation and/or sensing component size and cost may be reduced.